1. Field of the Invention
The present invention relates to novel polymer compositions and is more particularly concerned with novel syntactic foams having certain polyimides as the binding resin therein, and with methods for their preparation.
2. Description of the Prior Art
Syntactic foams, i.e. foams obtained by embedding a relatively low density hollow or solid spherical filler (microballoons or microspheres) in a plastic matrix, are well-known in the art. A variety of different types of spherical filler (fabricated from material such as glass and various synthetic polymers) and a variety of plastic matrices have been used; see, for example, U.S. Pat. Nos. 3,316,187, 3,325,341, 3,477,967 and 3,510,392.
We have now found that syntactic foams in which the polymer matrix comprises a particular type of copolyimide, are possessed of particularly valuable properties which render them useful in applications which will be described in detail hereafter.